Role of the carboxyl-terminal region in the activity of N-acetylglucosamine 6-o-sulfotransferase-1

J Biochem. 2004 Nov;136(5):659-64. doi: 10.1093/jb/mvh162.

Abstract

N-Acetylglucosamine 6-O-sulfotransferases (GlcNAc6STs) catalyze the transfer of sulfate from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to the C-6 position of non-reducing N-acetylglucosamine. N-acetylglucosamine 6-O-sulfotransferase-1 (GlcNAc6ST-1) is the first cloned GlcNAc6ST and is involved in the synthesis of the L-selectin ligand. We noticed conserved C-terminal segments among GlcNAc6STs and produced mutant enzymes to reveal the functional significance. Mutant enzymes were transiently expressed as fusion proteins with protein A in COS-7 cells, and some of them were purified to homogeneity by IgG Sepharose column chromatography. Deletion of a C-terminal segment (amino acid numbers 479-483) resulted in a complete loss of the activity, when assayed using GlcNAcbeta1-6ManOMe as a substrate. Upon site-directed mutagenesis of the C-terminal region, three mutants, L477A, L478A and L483A, exhibited reduced activity. The K(M )values for GlcNAcbeta1-6ManOMe of L477A and L478A were 4 times higher than the K(M) of the wild-type enzyme, while that of L483A was unchanged. On the other hand the K(M )for PAPS of L483A was 3 times higher than that of the wild-type enzyme, while the values of L477A and L478A were unchanged. Furthermore, the L477A mutant acted on a core 3 structure (GlcNAcbeta1-3GalNAc-pNP), while the wild-type enzyme does not. These results demonstrate a role for leucine residues in the C-terminal region in the enzymatic activity.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • COS Cells
  • Electrophoresis, Polyacrylamide Gel
  • Humans
  • Mutagenesis, Site-Directed
  • Mutation
  • Sulfotransferases / metabolism*
  • Sulfotransferases / physiology*

Substances

  • Sulfotransferases
  • carbohydrate sulfotransferases